This one is hard to explain, so I created an animated gif screen capture of it.
The yellow box works fine and was not generated in Blender. The blue plane that shows up part of the time was created in Blender and converted from the .blend file to .bam using blend2bam. The plane looks like it has no thickness but it does. I did not set a material in Blender so that Panda could control the color, and there is no transparency set. I don’t understand why the model is visible from some angles and not others. It has to be something with how I created the model or the blend2bam conversion, but I’m not sure where to look.
Ubuntu 18.04 64-bit